1. Field of the Invention
The present invention relates to an image processing technique and, more particularly, to an image restoration method and apparatus in which an image is restored by estimating the blur level of the image.
2. Description of the Related Art
Actuators used for an optical automatic focus (AF) function are generally large in size and thus may not be suitable for reducing the size of mobile phone cameras. In order to address this, a method capable of replacing the existing optical AF function while reducing the size of mobile phone cameras has been suggested. However, this method does not involve the use of an actuator, and thus, camera lenses need to be fixed. However, when the lens is fixed, the blur level of an image captured by the camera varies according to the distance between a subject and the lens. Thus, it is necessary to estimate the blur level of an image and restore the image using a point spread function (PSF) corresponding to the blur level.
One of the most well-known conventional image restoration methods is disclosed in the article “Image Restoration of Space Variant Blurs by Sectioned Method,” by H. J. Trussell and B. R. Hunt. This image restoration method includes calculating the blur level of a section using the central point of the section and a PSF. However, in this image restoration method, PSF is not estimated based on the blur level since it is assumed that the amount of blur is already known. Therefore, this image restoration method results in a relatively low accurate PSF estimation.
In the case of deblurring an image by using an inappropriate PSF, the image may not be properly deblurred, and various artifacts such as color defects or a ring effect may be generated in the image. It is thus very important to accurately estimate and refine PSF according to the type of image.